Tissue engineering holds the prospect of producing tissues in vitro to fill the need for tissue regeneration and provide faster and more complete healing for subjects. The clinical efficacy of synthetic-, allogeneic or xenogeneic-engineered tissues has been limited by various problems including thrombosis, immunorejection, chronic inflammation and poor mechanical properties of the tissues after implantation. In particular, cardiovascular tissue engineering and production of small blood vessels is needed.
The structural organization of cells and associated extracellular matrix (ECM) is critical to overall tissue function. Recapitulating the complex, highly organized structure of a target tissue is a key to achieve the unique functional characteristics of native tissue. However, this requires a system enables modulation of substrate physiochemical properties such as modulus, topology and surface chemistry. Currently available systems to grow engineered tissue do not offer the simultaneous control over all of these physiochemical properties. To recreate unique properties of a tissue, engineered tissue must mimic the complex structural characteristics of the tissue. Conventional tissue engineering approaches, i.e. seeding cells in pre-made artificial scaffolds, has limitations in reconstructing target tissue with specific structural characteristics. For example, in a vessel-like tissue, the structure defines its function: in the inner media layer, smooth muscle cell alignment in a herringbone pattern perpendicular to the flow direction allows for vessel tone control. Therefore, accurate mimicry of a tissue structure is key for generating functional and implantable engineered tissue.
Cell sheet technology has been suggested as an alternative to scaffold tissue engineering approaches because cell sheets preserve the integrated structure of cell and cell-secreted extracellular matrix (ECM) that accurately mimics 2D native tissue structure. Stacking patterned cell sheets according to the anatomy of the target tissue could not only produce biochemically and biomechanically equivalent three dimensional structure of the native tissue, but also restore the function of the tissue. Furthermore, because cell sheets could take a form of patches, tubes or folded structures depending on the tissue type, application potential of cell sheet technology is unlimited.
In the treatment of a severely damaged heart, cell transplantation utilizing a variety of stem cells has been attempted as an alternative therapy to heart transplantation which has been suffering from shortage of donors. Recently, based on such cell transplantation techniques, tissue transplantation techniques have been increasingly developed in which myocardial tissues are constructed three-dimensionally in vitro and then transplanted into a body. For example, various types of cell sheets have been successfully manufactured by using temperature-responsive culture dishes which are prepared by coating poly(N-isopropylacrylamide) (abbreviated to “PIAAm”) on the surfaces of commercial polystyrene culture dishes with electron beams. In particular, as for myocardial cells, it has already been reported that myocardial tissue masses available as transplants can be developed by overlaying the thus prepared multiple myocardial cell sheets (Japanese Patent Application Laid-open No. 2003-38170, WO 01/068799, Simizu et al.: Fabrication of pulsatile cardiac tissue grafts using a novel 3-dimensional cell sheet manipulation technique and temperature-responsive cell culture surface: Circ Res. 2002; 90:e40-e48). The thus prepared myocardial tissue mass is found to exhibit electrical activities similar to those of normal myocardial tissues in vitro and in vivo. However, the heat-sensitive substrate is expensive and the temperature used to displace the cells from the substrate can damage the cells.
Accordingly, there is an urgent need for cost-effective, simple and reliable cell sheet harvest and transfer system that can be used without damaging cell layer integrity or viability on removal of the substrate or scaffold.